The present invention relates to a transmitter, a computer system, and an opening/closing structure. More particularly, the present invention relates to a technique for transmitting a high-frequency signal or energy efficiently through a movable part or portion.
Some general electrical apparatus are configured by a base unit and a door/lid attached to the base unit respectively. And, for some electric apparatus, the door/lid is provided with a display, an input device, and an antenna respectively. FIG. 19 shows a schematic structure of a lap-top personal computer (PC). FIG. 20 shows a cross sectional view of the lap-top PC shown in FIG. 19. Generally, a lap-top PC has a base unit part 101 and a lid part 104 attached to the base unit part 101 by movable joints 103. The base unit part 101 is provided with, for example, a keyboard 102, a mother board (not illustrated), etc. The lid part 104 is provided with a flat-surface display 105, etc. When the lap-top PC has such a structure, the lid part 104 can be opened and closed to the base unit part 101 when the PC is not used and/or it is carried about, for example. The opening angle of the lid part 104 can be adjusted so as to make it easier to watch the flat-surface display screen.
When the lap-top PC is structured as shown in FIG. 19, the lid part 104 is provided with an antenna 191. The antenna 191 is used, for example, for a wireless link for the PC to such a communication network as a LAN (Local Area Network). Otherwise, the antenna 191 is used to send/receive data to adopt (accommodate) the Bluetooth standards, etc. A radio device 108 is installed in the base unit part 101. The radio device sends/receives a high-frequency signal to/from the antenna 191. The reason why the radio device 108 is installed in the base unit part 101 is to meet the requirement mainly for thinning the lid part 104 more in structure or for making it easy to install the radio device 108 in the base unit part 101. Therefore, the radio device 108 installed in the base unit part 101 must be coupled to the antenna 191 in some way. A signal cable 192 is usually used for the connection between the antenna 191 and the radio device 108. And, the signal cable 192 is usually a thin coaxial cable. The cable is laid by passing through a movable joint 103 so as to improve external appearance and reliability.
However, the above structure is confronted with the following problems when the signal cable 192 passes through a movable joint 103. Because the signal cable 192 passes through a movable joint attaching the lid part 104, or because it passes very close to the joint, the signal cable 192 itself is required to be thin and flexible. And, such a PC structure will eventually damage the signal cable as the lid part is opened and closed repetitively.
When such a thin and flexible signal cable 192 is bent repetitively, the dielectric material properties of the cable might be changed, thereby, the cable""s electromagnetic wave transmission loss (usually in a microwave frequency band) is likely to increase. In addition, the transmission loss might be increased at the bent portion of the signal cable 192, although the loss depends on the bending angle.
And, in order to pass the signal cable 192 through a movable joint 103 in such a way, meticulous care must be used during the assembly process and accordingly, complicating the assembly process.
The above-described problems will also arise from electrical apparatus other than such lap-top personal computer. Concretely, when a signal cable is used to connect the base unit part to the lid part in a lap-top PC provided with such the base unit and the lid, the signal cable is often damaged due to the repetitive bending just like in the above case.
Under such circumstances, it is an purpose of the present invention to provide an electrical apparatus configured so as to avoid such the cable damage and other problems caused by the transmission structure that uses a signal cable for transmitting a high-frequency signal unavoidably between the base unit part and the lid part or door part.
The basic concept of the present invention is realized by a technique that a pair of antennas are disposed closely to each other, thereby a high-frequency signal or energy is transmitted at a low transmission loss between those antennas. The present invention employs such a transmission structure that uses a pair of antennas disposed closely to each other instead of the conventional method that uses a signal cable for transmitting an electrical signal and uses a connector for connection of such a signal. Hereinafter, the outline of the present invention will be described.
The transmitter of the present invention includes a first antenna and a second antenna disposed so as to face the first antenna and be separated therefrom. A high-frequency signal or energy is transmitted between the first and second antennas. The distance between the first and second antennas is decided to be xcex/8 or under (xcex: a wavelength of the high-frequency signal or energy) or the imaginary part of the mutual impedance between the first and second antennas is decided to be actually 0. In this specification, the high-frequency is defined as a frequency (over the VHF band) of 10 MHz, for example, 30 MHz or over.
In the transmitter, the second antenna is attached to the lid or door that opens/closes to the base unit to which the first antenna is coupled. While the lid or door is closed, the second antenna is disposed so as to face the first antenna. The first and second antennas may be dipole antennas, folded antennas, or slot antennas. The slot antenna is at times referred to as a slit antenna.
In the transmitter, the second antenna is disposed on a coaxial cylinder whose axis is assumed to be the center of the first antenna rotationally on the concentric cylinder around the axis. At this time, the first antenna may be a dipole antenna or cylindrical slot antenna (slit antenna) and the second antenna may be a dipole antenna, folded antenna, or cylindrical slot antenna (slit antenna).
In the transmitter, a radio device or signal generator may be coupled to the first antenna and a third antenna or signal processor may be coupled to the second antenna via a signal cable.
The transmitter may be employed for a lap-top computer system. It may also be employed for such an opening/closing structure as a door, etc.